<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>my html5</title>
    <style>
        .c1 {
            width: 600px;
            border: 1px dashed purple;
        }
        img {
            width: 100%;
            visibility: hidden;   /*设置可见性为不可见*/
        }
        .c1:hover img {     /*设置鼠标悬停在.c1上时，它里面的img标签*/
            visibility: visible;  /*设置可见性为可见*/
        }
    </style>
</head>
<body>
<div class="c1">
    <img src="http://pic1.win4000.com/wallpaper/3/584a8ae6eeb4f.jpg">
</div>
</body>
</html>